1. Field of the Invention
The invention relates to a mast for a source of electromagnetic waves, comprising a number of peripheral rods extending in a vertical direction, the peripheral rods being mutually connected by transverse rods and forming a space for accommodating the electromagnetic wave source in, or on top of, the mast.
2. Description of the Related Art
Such masts are known, and are used in telecommunication, particularly as radio masts for the benefit of mobile telecommunication. Such masts serve as a support for antenna configurations, and offer protection to sources of electromagnetic waves mounted in the top of the mast, such as antennae, microwave beam transmitters and the like.
Such masts furthermore offer a beautiful architectonic design which, if so desired, may be very well fit into the urban design.
Such masts have the drawback, however, that on account of their shape, they are sensitive to uncontrollable natural vibrations in the event of hypercritical wind speeds. Said phenomenon occurs in the event of wind speeds from 30 to 40 km/h., is known as xe2x80x9cgallopingxe2x80x9d, and has a strongly negative effect on the functionality and the structural integrity of the mast. It is noted that the effect of galloping differs from the one of ordinary vibrations as a result of the wind, which is understood by experts.
In the event of structural galloping, small movements of the structure perpendicularly to the direction of the wind are amplified by the forces of the wind on the structure.
The phenomenon may particularly occur in the event of flexible structures having a triangular cross section. With such structures, a small deviation from the equilibrium position is amplified by a negative lifting force perpendicular to the direction of the wind.
The energy added by the wind manifests itself in an uncontrollable increase of the deviation.
In practice, galloping manifests itself with radio masts having certain antenna configurations and with radio masts having a triangular cross section bearing a lining.
The invention now overcomes said objections, and the mast according to the invention is characterised for that purpose by the mast being provided with a stabilisation device for reducing uncontrollable natural vibrations in the event of hypercritical wind speeds, said stabilisation device being accommodated in, or on top of, the mast.
In this manner, the natural vibrations in question are reduced to an acceptable level, and the energy added by the wind is adsorbed before this results in uncontrollable travels of the mast.